And Tamerlan Tsarnaev had already demonstrated a violent streak outside of the ring: In 2009, he was charged with domestic violence after admitting to police that he had slapped a former girlfriend, who then called police in hysterics. The charge was later dismissed after a jury trial.
Younger brother Dzhokhar, meanwhile, had been captain of the Cambridge Rindge and Latin wrestling team and was also known as an adept boxer, according to Zolan V. Kanno-Youngs, a neighbor, friend, and former classmate.
And during the months before the killings, it is clear that Tsarnaev had become increasingly radicalized in his religious and political beliefs.
Maret Tsarnaeva, Tsarnaev’s aunt, told reporters at a news conference that her nephew went from praying no more than once a day to praying five times a day. And a neighbor and family friend in Cambridge said Tsarnaev had become a devout Muslim within the past few years.
“He started talking about religion,” said the family friend, who asked not to be identified. “He grew a long beard.”
When the friend joked about the beard, he said, Tamerlan became upset, asking, “Why are you making fun of my religion?”
It appears that Tsarnaev also toyed with extremism online. A YouTube account created in Tamerlan Tsarnaev’s name in August 2012 includes a video dedicated to the prophecy of the Black Banners of Khurasan, which is apparently embraced by Islamic extremists.
In another video, featured on a play list titled “terrorists,” a speaker holds an assault rifle and wears camouflage fatigues while flanked by armed men wearing masks.
The relative of the Waltham homicide victim interviewed by the Globe said he and others hope their recent appeal to police about Tamerlan Tsarnaev’s possible role in the killings will lead to a conclusion of the case.